An SIM (Subscriber Identity Module) card stores information of a user of the corresponding digital mobile terminal, a key for encryption, a telephone book of the user and so on. The mobile terminal can be used by the user for communication only when the SIM card is plugged therein.
The SIM card is provided with metal contacts, which connect with terminals of an SIM card connector of the mobile terminal to allow for communication. When the SIM card is completely plugged into the SIM card connector, each of the metal contacts connects to just one terminal. However, in the process of plugging the SIM card into or removing the SIM card from the SIM card connector, it is likely that some terminals of the SIM card connector connect to more than one metal contact simultaneously. If, in this case, the SIM card connector is still kept energized, there will be a risk of damaging the SIM card due to a short-circuit. For example, refer to FIG. 1, which is a schematic view illustrating operations of plugging or removing the SIM card in the prior art. After the SIM card 10 is completely plugged into the SIM card connector (not shown), the metal contacts 101 of the SIM card 10 are in one-to-one correspondence with the terminals 102 of the SIM card connector. In the process of removing the SIM card 10, it is likely that one terminal 102 connects to two metal contacts 101 simultaneously because of the large touch areas between the terminal 102 and the metal contacts 101. If, in this case, the terminal 102 is still connected with the power supply, then the SIM card 10 will be short-circuited.
In mobile terminals of the early stage, the structure design is such that the battery can be installed only after the SIM card has been plugged and, on the other hand, the SIM card can be removed only after the battery has been removed, so there is no risk of short-circuit of the SIM card. However, as the mobile terminals are developing towards an integrated form, built-in batteries have become a general trend. Correspondingly, there might be cases where the SIM card is hot plugged in or removed with the mobile terminal being powered on.